Conventionally, tracking of the position of a physical object such as a person displayed in video has been performed using a particle filter (see Patent Literature 1 and Non-Patent Literature 1, for example).
In the technology described in Patent Literature 1 and the technology described in Non-Patent Literature 1 (hereinafter referred to collectively as “the conventional technology”), a feature of an image of an object in video is first found. In the conventional technology, a plurality of particles indicating candidates for the position of an object at time t following the position of the object at time t-1 are generated, and feature mapping is performed between each time t particle and a time t-1 object position. Then, in the conventional technology, the likelihood of each particle being the time t object position is calculated from the corresponding similarity. Then, in the conventional technology, the position of the particle with the highest likelihood is estimated as the object position at time t for each object. By this means, the conventional technology enables the position of the same object to be tracked continuously.
Also, in the technology described in Patent Literature 1, in particular, an above likelihood is corrected using a color feature when a feature is a shape feature indicating a contour curve of an object. Specifically, in the technology described in Patent Literature 1, a color feature that is a color histogram of an area within a contour curve, for example, is first calculated for each particle. Then, in the technology described in Patent Literature 1, similarity between an object color feature color histogram and a color histogram of each particle is calculated by means of histogram intersection. Following this, the technology described in Patent Literature 1 corrects an above likelihood based on a calculation result. By this means, with the technology described in Patent Literature 1, even if a different object with a similar contour curve is positioned in the vicinity of a target object, the possibility of that different object being tracked by mistake can be reduced.